An internal combustion engine requires different amounts of intake air under different operating conditions. For example, in order to increase engine speed, the air handling system may be required to increase (boost) the pressure (or density) of intake air so as to provide more oxygen to burn more fuel, thereby increasing the power delivered by the engine. To pressurize intake air on demand, the air handling system may include a supercharger, which is an air compressor driven by a mechanical coupling to an engine crankshaft. However, if a supercharger is designed for operation at low engine speeds, the supercharged intake air pressure at high speeds may be higher than necessary for optimal operation. Similarly, if the supercharger is designed for operation at high engine speeds, the supercharged intake air pressure will be insufficient to generate sufficient torques at low speeds. Therefore, there is need for a drive device that allows the supercharger to operate efficiently at both high and low engine speed conditions.
In modern vehicles such as trucks and automobiles, engine compartment space for auxiliary devices such as superchargers may be very limited. The room available for a supercharger drive may be further limited due to a need to locate the supercharger in close proximity to a crankshaft for coupling. So it is desirable that a multi-speed drive for a supercharger be as compact as possible while providing functionality which enables multi-speed supercharger operation. This is achieved in the supercharger drive embodiments described below by using a planetary gear-set and a multidisc clutch mechanism mounted for rotation on a stationary shaft.